Iterating in Dataframe's Columns using column names as a List and then looping through the list in Python

Question

Im trying to LabelEncode particular columns of a Dataframe. I have stored those column names in a list(cat_features). Now i want to use a For loop to iterate through this list's elements (which are strings) and use those elements to access dataframe's column. but it says

TypeError: argument must be a string or number

Since Im accessing the element of the list which is already a string. so i dont understand why it throw that error. Please help me understand why it doesn't work and what can I do to make it work.

cat_features = [x for x in features if x not in features_to_scale]

from sklearn.preprocessing import LabelEncoder

for feature in cat_features:
    le = LabelEncoder()
    dataframe[feature] = le.fit_transform(dataframe[feature])

do u have a list as an element in your columns? – Akshay Sehgal Jul 29 '20 at 13:30 — Akshay Sehgal, Jul 29 '20 at 13:30

Akshay Sehgal · Accepted Answer · 2020-07-29T13:45:40.253

0

The error means that one or more of your columns contains a list/tuple/set or something similar. For this, you will need to convert the list/tuple to a string before you can apply a label encoder

Also, instead of a loop, you can first filter your data frame by the features you need then use apply function -

df = main_df[cat_features]
df = df.astype(str)     #This step changes each column to string as label encoder cant work on lists/tuples/sets

lb = LabelEncoder()
df.apply(lb.fit_transform)

Later you can combine this data frame with the remaining continuous features.

edited Jul 29 '20 at 13:45

answered Jul 29 '20 at 13:26

Akshay Sehgal

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Okay, I checked the dataset. there is one column that contains value as "C(all)" maybe that's causing the problem. – Austin Spark Jul 29 '20 at 14:03
the ```df.astype(str)``` should solve your problem though. Did you try my code? – Akshay Sehgal Jul 29 '20 at 14:04
Yes Sir! Your code worked well. More than that you gave me the root of the problem, which I can now tackle in different ways. I highly appreciate it. Thanks – Austin Spark Jul 29 '20 at 14:23

Iterating in Dataframe's Columns using column names as a List and then looping through the list in Python

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